Chemical, biological, agricultural and related materials are examined using various analytical methods. These methods include techniques for separating or identifying samples and their individual components on various media, such as electrophoresis and thin layer chromatography (TLC), or related charts obtained following chromatography, immunoblots, densitometric scanning, dot blots, and related techniques. With electrophoresis and TLC, a sample is placed at one end of an assay medium such as a polyacrylamide gel or silica gel plate, and an electric field or organic solvent is applied to cause the sample to migrate and separate according to size across the medium. With immunoblots and dot blots, a sample is transferred, with or with prior separation, to an inert media prior to chemical analysis.
In electrophoresis, polyacrylamide, agarose gel or other gel matrices are prepared by pouring a liquid mixture into a chamber, and a comb-shaped form is then inserted to form discrete wells in the upper end of the gel. Test samples are then placed into the wells, and a uniform electric potential is applied to the gel. A mixture of molecular weights standards is typically placed into one well as a control. The negatively charged molecules migrate from the wells in lanes toward the anode at the lower end of the gel slab. Individual components of the samples and standards become separated as bands as smaller molecules move rapidly through the gel and larger molecules move slowly or remain at the upper end of the gel slab. Upon completion of the electrophoretic separation, the gel slab is removed from the chamber and stained with an appropriate dye or other visualizing agent, and illuminated to reveal the separated molecules on the gel. Optionally, the molecules on the gel may be transferred to a second assay medium such as a nitrocellulose membrane, for further analysis by Southern blot, Northern blot, Western blot, isoelectric gels, autoradiographic films, elispots, slot/dot blots, densitometric scans, or other like assay.
The assay medium is then photographed to make a permanent record of the results of the separation. The photograph is subsequently marked on its face to show the lanes associated with each sample, and identify the locations of the separated bands of molecules on the assay medium, usually according to molecular weight as compared to the molecular weights standards, used as the control.
At present, a photograph is marked using permanent ink, radioactive ink, non-radioactive phosphorescent or fluorescent markers, dry-transfer symbols, tape labels, or a frame with attached labels. One commercially-available product from Diversified Biotech, IDENTI-KIT.TM., includes adhesive labels, numbers and letters for radioactive work which are either permanently affixed by light development following development of the X-ray film, or affixed after development of the X-ray film at which time the markers may be reused.
Marking individual photographs with lane information and sample locations is an arduous task, particularly where a scientific report or publication contains numerous photographs of electrophoresis gels. In addition, a written record must be kept of the locations of the sample lanes, and positions of the molecular standards, or other pertinent information, so that this information can later be transferred to the photograph. Another disadvantage is that if more copies of a marked photograph are needed, the marked copy must be either rephotographed and printed wherein there is often a reduction in clarity of the photograph, or another copy of the original photograph must be labeled with a second set of markers. Also, markers that are permanently affixed to the photograph cannot be reused in multiple applications, and releasably-adherent markers have a limited lifetime for reuse. Still another drawback of present marking systems is that a photograph with an error in the marking must be discarded and the marking process repeated to prepare a newly marked photograph. Also, if it is desirable to eliminate a sample lane from the assay medium or rearrange the lanes in relation to each other, the photograph must be cut up, carefully reassembled, and then rephotographed.
Therefore, an object of the invention is to provide an apparatus and method, to facilitate annotating an assay media containing samples. Another object is to provide an apparatus for use in multiple applications, and which shorten the annotating process. Yet another object is to provide an accurate and quick permanent record of assay results.